WO2019211088A2

WO2019211088A2 - Electronic monitoring system for hydrostatic travel drives and travel drive with electronic monitoring system

Info

Publication number: WO2019211088A2
Application number: PCT/EP2019/059694
Authority: WO
Inventors: Matthias Mueller; Heinz Hense; Juergen Feig; Peer MUMCU; Ronny Herrmann; Veronica ARENAS
Original assignee: Robert Bosch Gmbh
Priority date: 2018-05-04
Filing date: 2019-04-15
Publication date: 2019-11-07
Also published as: CN112041596B; CN112041596A; EP3788279A2; EP3788279B1; US20210372522A1; WO2019211088A3; US11821511B2; DE102018206908A1

Abstract

A monitoring system for a travel drive and a travel drive with a monitoring system are disclosed. Acceleration is determined by means of a rotational speed sensor of a hydrostatic motor, and in addition at least one signal from apressure sensor mounted on the at least one working line that connects the pump to the motor of the hydrostatic travel drive is evaluated. The pressure sensor is preferably arranged on the at least one working connection of the pump. The additional pressure signal makes it possible to evaluate in a reliable manner whether the hydrostatic travel drive generates an unwanted drive torque.

Description

Electronic monitoring system for hydrostatic travel drives and traction drive with electronic monitoring system

description

Technical area

The present disclosure relates to an electronic monitoring system for hydrostatic travel drives for vehicles for realizing safety functions and a corresponding travel drive.

DE 10 2008 021 313 A1 discloses a hydraulic component control apparatus and a method for controlling hydraulic components such as e.g. Travel drives of mobile machines. A control function and a monitoring function monitor each other.

From the state of the art electronic monitoring systems are furthermore known in which the affected hydrostatic drive is monitored by the speed signal of the hydrostatic motor to realize safety functions. In addition, traction drives are known in which the drive current for the hydrostatic pump is monitored. Related surveillance concepts are known in the automotive industry as "EGAS surveillance concept" or "3-plane concept".

For the standardized safety function "safe standstill" which can also be described as safe lack of drive, driver inputs are evaluated, for example the accelerator pedal position and the selected direction of travel. After the driver, for example when the vehicle is stationary, by releasing the accelerator pedal or by selecting the direction of travel "neutral" requires standstill or lack of drive, the hydrostatic

i Traction drive generate no active drive torque, so that the vehicle does not start unintentionally.

In the above solution, only the speed signal of the hydrostatic motor is used for monitoring. With this signal can not be distinguished whether the vehicle moves unintentionally, because the hydrostatic drive generates an active drive torque, which should be recognized as a fault condition, or if the vehicle only due to external forces such as the downhill force or inertia in basically allowed to move, which is not a fault condition. Thus, the detection of fault conditions is restricted in the case of monitoring systems from the prior art and can be used meaningfully only for certain types of vehicle (for example municipal vehicle with parking brake). In addition, use is for very dynamic vehicles, such as e.g. Wheel loader in the heap, not possible because faulty states and not faulty states can not be distinguished.

The invention is intended to improve the electronic monitoring system of a traction drive in such a way that it also reduces error conditions in hitherto problematic driving situations, e.g. when rolling on a slope and in dynamic driving maneuvers of vehicles, e.g. when rolling out of wheel loaders, reliable and robust recognizes.

These objects are achieved by an electronic monitoring system according to claim 1 and by a hydrostatic vehicle drive according to claim 5.

The claimed electronic monitoring system is designed to monitor a hydrostatic drive of a vehicle. The hydrostatic drive has an operating element, via which a standstill signal or a drive-less signal can be transmitted to an electronic control unit of the monitoring system. The traction drive also has a hydrostatic pump and a hydrostatic motor. The monitoring system has a speed sensor for direct or indirect detection of an engine speed, from which according to the invention an acceleration of the engine and / or of the vehicle can be determined via the control unit. According to the invention, the monitoring system also has at least one first pressure sensor via which a first pressure signal of a first working line of the traction drive can be transmitted to the control unit. This means a drive state and / or a drive-less state of the drive concerned determined. The drive state may also be referred to as the active state and the drive-less state as the passive state of the traction drive. The electronic monitoring system of the prior art is thus improved in that it reliably and robustly detects fault conditions even in hitherto problematic driving situations, eg when rolling on a slope and during dynamic driving maneuvers of the vehicle concerned, for example when coasting wheel loaders.

Assuming the driver brings the vehicle to a halt on a steep slope and continues to call for standstill or lack of drive. When the vehicle starts to move again due to the downhill force, the monitoring system according to the invention can recognize, on the basis of the significant acceleration and the non-significant pressure signal of the working line which feeds the engine, that there is no fault of the hydrostatic drive because this does not affect the movement of the vehicle caused. Previous solutions can only be used if a parking brake prevents such situations.

In the previous solution, in which the drive current is monitored for the hydrostatic pump, there is also the disadvantage that they can not detect errors that are outside the electronic control, so for example in the control unit of the pump. The monitoring system according to the invention can also detect fault conditions that are caused by faults outside the electronic control.

A defect within the pump control, which ensures that the pump swings out and generates an undesired drive torque, can be detected by the evaluation of the at least one pressure sensor, since in this case a significant pressure signal of the serving as an inlet to the engine working line is detected. In the previous solution, in which only the drive currents were monitored, such errors could not be detected.

As mentioned above, the detection of the engine speed by the speed sensor can also be done indirectly. This is the case, for example, if a mechanical gearbox is installed between the hydrostatic motor and a differential gearbox. For example, there are often two mechanical gears, one transport gear (fast) and one operation (slow), between which can be switched at standstill (standstill gearbox). But there are also mechanical gearboxes that can be used while driving (eg "shift-on-fly" gearbox). The speed sensor can then be installed on the output shaft of the gearbox or in the transmission. Although the speed sensor then does not measure the speed of the hydrostatic engine, it does, for example, measure the transmission output speed, but the invention still works the same if the engine speed is replaced by the transmission output speed.

In addition, two hydrostatic motors can be interconnected with a mechanical summation gearbox C.2 + 1 summation gearbox "). The speed sensor can also be installed here on the output shaft of the gearbox or in the transmission. The invention is also applicable here when using the transmission output speed instead of the engine speed. The two hydrostatic engines with the summation gear can be treated effectively like a single hydrostatic engine.

Finally, there are variants in which the hydrostatic motors are installed directly on the wheel of the vehicle. Here, in principle, only the axle drive is eliminated.

In a particularly preferred development, the monitoring system according to the invention has a second pressure sensor, via which a second pressure signal of a second working line can be transmitted to the control unit. This can be monitored with the monitoring system according to the invention, a bidirectional drive with a closed hydraulic circuit. The monitoring system can determine that the second working line is under significant pressure, thus also detecting active reverse driving of the traction drive to be monitored. If it is requested by the driver via the control element standstill or lack of drive, the error is detected.

Preferably, a forward signal and a reverse signal from the operating element to the electronic control unit can be transmitted. Then, with the second pressure sensor on the second working line, an active reverse drive for a forward signal of the operating element or an active forward drive for a reverse signal of the operating element can be detected. Thus, the monitoring system according to the invention also provides a "Safe Direction" and a "Safe Reversing" function. The claimed hydrostatic drive for a vehicle has an operating element, via which a standstill signal or a drive-less signal can be transmitted to an electronic control unit of an electronic monitoring system. The traction drive has a hydrostatic pump and a hydrostatic motor. The monitoring system has a speed sensor for detecting an engine speed from which, according to the invention, an acceleration of the engine and / or the vehicle can be determined via the control unit. According to the invention, the monitoring system has a first pressure sensor, via which a first pressure signal of a first working line of the travel drive can be transmitted to the control unit. In this way, a drive state and / or a drive-less state of the travel drive can be determined. The drive state can also be referred to as the active state and the drive-less state as the passive state of the travel drive according to the invention. The advantages of the drive according to the invention correspond to those of the above-described monitoring system.

The traction drive according to the invention has in a particularly preferred bidirectional development of a closed hydraulic circuit with a second working line. Then, the monitoring system has a second pressure sensor, via which a second pressure signal of the second working line can be transmitted to the control unit. Thus, the monitoring system is also bi-directional, and can determine that the second working line is under significant pressure, and so on. recognize active reverse drive of the drive according to the invention. If it is requested by the driver via the control element standstill or lack of drive, the error is detected.

In the monitoring system according to the invention and in the traction drive according to the invention, a pressure difference between the first and the second pressure signal can preferably be determined by the control unit. Then an error can be determined by the control unit if the standstill signal or the drive-less signal is transmitted from the operating unit to the control unit, and if in addition the following three conditions are met:

- Engine speed is greater than zero, from which a forward drive is concluded, and

- Pressure difference is greater than or equal to a reference value for the pressure difference, and

- Acceleration (of the engine or the vehicle) is greater than a reference value for the acceleration. In the monitoring system according to the invention and in the travel drive according to the invention, an error can also be determined if the standstill signal or the drive-less signal is transmitted from the operating unit to the control unit, and if in addition the following three conditions are met:

- Engine speed is less than zero, from which a reverse drive can be inferred, and

- Pressure difference is less than or equal to the above but negative reference value for the pressure difference, and

- Acceleration is less than the above but negative reference value for the acceleration.

In the monitoring system according to the invention and in the traction drive according to the invention, the operating element from which the standstill signal or the drive-less signal is transmitted to the control unit, for. B. a direction lever in a neutral position or an accelerator pedal in a zero position or an inch pedal in a maximum position.

In the monitoring system according to the invention and in the travel drive according to the invention, the pump can be an ET pump. Then a non-rigid and not pedal-controlled control of the ET pump via a control pressure is preferred. Other types of activation, such as An EP pump is also possible.

Figure 1 shows the embodiment of the drive according to the invention for a mobile machine, which may be, for example, a wheel loader. The mobile working machine has a diesel engine 1, to whose crankshaft (not shown in more detail) an axial piston pump 2 adjustable in its stroke volume is coupled. This supplies in a closed circuit via two working lines 4 _A , 4 B, a motor 6 whose output shaft is coupled via a differential gear 8 to two wheels 10. The pump 2, the two working lines 4 _A , 4 B and the motor 6 are attributable to the traction drive according to the invention.

An accelerator pedal 12 is mechanically coupled to the diesel engine 1 in the embodiment shown. Furthermore, the drive according to the invention has a central data line 14, to which an electronic control unit 15 is connected. Position data or position signals of the accelerator pedal 12, a direction lever 11 and an inching pedal 17 are transmitted via the central data line 14. The inching pedal 17 serves to favor consumers of the mobile working machine over the travel drive.

Furthermore, pressure signals of a first pressure sensor 16A and of a second pressure sensor 16B are transmitted to the control unit 15 via the central data line 14. The two pressure sensors 16A, 16B are arranged at the two main ports of the pump 2 and detect the working pressure of the respective working line 4A, 4B.

Furthermore, a pump speed np is transmitted to the control unit 15 by a speed sensor (not shown), and an engine speed HM is transmitted by a speed sensor 18M.

From the control unit 15, a control pressure signal Pst is transmitted via the central data line 14, wherein the pump 2 is designed as an ET pump.

In a preferred alternative embodiment, the pump 2 is not driven via the central data line 14, but via two separate electrical lines (not shown in detail), are transmitted via the two control current signals for solenoid valves of the pump 2.

As an example, the safety function "safe standstill" or safe lack of drive of the illustrated embodiment of the drive according to the invention will be explained. The safety function prevents the driver from unwanted active acceleration of the mobile work machine by the drive.

The following controls of the driver are evaluated by the control unit 15:

Direction of travel lever 11,

• accelerator pedal 12 and

• inch pedal 17. The driver requests standstill or lack of drive if at least one of the following conditions is met:

• Direction of travel lever 11 is in "neutral" position,

• Accelerator pedal 12 is in zero position or

• Inch pedal 17 is in maximum position.

Other controls, e.g. a creep potentiometer and its evaluation are also possible.

In particular, the following sensors are evaluated:

• speed sensor 18M on hydrostatic motor 6 (symbol for engine speed: HM),

• First pressure sensor 16 _A at the hydrostatic pump 2 or at the first one

Working line 4 _A (symbol for the first pressure: P _A ) and

Second pressure sensor 16B on the hydrostatic pump 2 or on the second

Working line 4B (symbol for the second pressure: PB).

From the speed signal H _M is also calculated numerically the acceleration a. More precisely, the rotational acceleration of the motor 6 is determined and, if necessary, numerically the acceleration of the mobile work machine is calculated. From the two pressure signals P _A and P _B , the pressure difference Dr is still formed.

The pressure difference Dr is always calculated by convention so that a positive pressure difference Dr means an active driving torque in the forward direction. This is important for the formulation of the error condition for the pressure difference. Depending on the installation position of the pressure sensors 16 _A , 16 _B and tubing of the hydrostatic drive is thus Dr = P _A - P _ß or Dr = PB - P _A.

If the driver requests standstill or lack of drive via one of the above-mentioned control elements, and one of the following two conditions is fulfilled, then there is an error which is detected by the monitoring system according to the invention. 1. (n _M > 0) and (Dr> = Ap _Ref ) and (a> -a _Ref )

2. (n _M <0) and (Dr <= -Ap _Ref ) and (a <a _Ref )

Dr _Ref and a _Ref are reference values for pressure difference and acceleration, which may also depend on time. The first condition means that the mobile work machine is moving forward, and there is a significant or too large pressure difference Dr (relative to the reference value Ap _Ref ) from which a significant or too large forward driving torque is inferred (relative to the reference value), and the acceleration a forward is significant or too large (relative to the reference value -a _Ref ).

In the case of the closed-loop bidirectional travel drive shown in FIG. 1, the second condition applies analogously to reverse travel. The second condition therefore means that the mobile work machine moves backwards, and there is a significant or too large pressure difference Dr (relative to the reference value -Ap _Ref ). From this, a significant or too large driving torque to the rear (relative to the reference value) is inferred. In this case, the acceleration a to the rear is significant or too large (relative to the reference value a _ref ).

In this way, when the error is detected by the monitoring system, the electronic control unit 15 shuts off all electrical outputs to finally shut off the travel drive and bring the mobile work machine into a safe state.

Disclosed are a monitoring system for a travel drive and a travel drive with a monitoring system. By means of a speed sensor of a hydrostatic motor, an acceleration is determined, and additionally at least one pressure sensor is evaluated, which is installed on the at least one working line which connects the pump to the motor of the hydrostatic drive. Preferably, the pressure sensor is arranged on the at least one working port of the pump. With the help of the additional pressure signal can be reliably assessed whether the hydrostatic drive generates an unwanted driving drive torque or not.

Claims

claims

1. An electronic monitoring system for a hydrostatic drive having an operating element, via which a standstill signal or a drive-less signal can be transmitted to an electronic control unit (15) of the monitoring system, and a hydrostatic pump (2) and a hydrostatic motor ( 6), wherein the monitoring system comprises a speed sensor (18M) for detecting an engine speed (PM), characterized in that from the engine speed (H _M ) via the control unit (15) an acceleration (a) of the motor (6) can be determined , and in that the monitoring system has a first pressure sensor (16A) via which a first pressure (PA) of a first working line (4A) of the travel drive can be transmitted to the control unit (15), whereby a drive state and / or a drive lot State of the traction drive can be determined.

2. Monitoring system according to claim 1 with a second pressure sensor (16B) via which a second pressure (PB) of a second working line (4B) to the control unit (15) can be transmitted.

3. Monitoring system according to claim 2, wherein from the control unit (15) a pressure difference Dr between the first pressure (PA) and the second pressure (PB) can be determined, and wherein from the control unit (15) an error can be determined when of the Operating unit, the standstill signal or the drive-less signal is transmitted to the control unit, and if in addition the following three conditions are met: Engine speed (PM)> 0 and

Pressure difference (Dr)> = Ap _Ret and

Acceleration (a)> -a _ref .

4. Monitoring system according to claim 2 or 3, wherein from the control unit, a pressure difference Dr between the first pressure (PA) and the second pressure (PB) can be determined, and wherein from the control unit (15) an error can be determined, if by the operating unit the standstill signal or the driveless signal is transmitted to the control unit, and if in addition the following three conditions are met: Engine speed (PM) <0 and Pressure difference (Dr) <= -Äp _Ref and

Acceleration (a) <a _ref .

5. hydrostatic drive having a control over which a stoppage

Signal or a non-drive signal to an electronic control unit (15) of an electronic monitoring system is transmitted, wherein the traction drive comprises a hydrostatic pump (2) and a hydrostatic motor (6), and wherein the monitoring system, a speed sensor (18M) for detecting an engine speed (HM), characterized in that from the engine speed (HM) via the control unit (15) an acceleration (a) of the motor (6) can be determined, and that the

Überwachu ngssystem a first pressure sensor (16A), via which a first pressure (PA) of a first working line (4A) of the traction drive to the control unit (15) is communicable, whereby a drive state and / or a non-powered state of the traction drive can be determined.

6. Drive according to claim 5, which has a closed circuit with a second

Working line (4B), wherein the monitoring system, a second pressure sensor

(16B), via which a second pressure (PB) of the second working line (4B) can be transmitted to the control unit (15).

7. Drive according to claim 6, wherein from the control unit (15) a pressure difference Dr between the first pressure (PA) and the second pressure (PB) can be determined, and wherein from the control unit (15) an error can be determined when of the Operating unit, the standstill signal or the drive-less signal is transmitted to the control unit (15), and if in addition the following three conditions are met:

Engine speed (PM)> 0 and

Pressure difference (Dr)> = Ap _Ref and

Acceleration (a)> -a _ref .

8. Drive according to claim 6 or 7, wherein from the control unit (15) a pressure difference Dr between the first pressure (PA) and the second pressure (PB) can be determined, and wherein from the control unit (15) an error can be determined, if from the operating unit, the standstill signal or the drive-less signal is transmitted to the control unit of the monitoring system, and if additionally satisfies the following three conditions are:

Engine speed (PM) <0 and

Pressure difference (Dr) <= -Äp _Ref and

Acceleration (a) <a _ref .

9. Drive according to one of claims 5 to 8, wherein the operating element is a direction lever (11) in a neutral position, or wherein the operating element is an accelerator pedal (12) in a zero position, or wherein the operating element is an inch pedal (17 ) is in a maximum position.

10. Drive according to one of claims 5 to 9 wherein the pump (2) is an ET pump, and wherein a non-rigid and non-pedal-driven control of the ET pump via a control pressure (pst) is provided.